JPH0253751B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the fault point when a ground fault occurs in an overhead high-voltage distribution line for some reason, resulting in a power outage.

The following method was considered as an example of a method for searching for this type of accident point. That is, a carrier signal of about 100Hz to 1000Hz is placed on an overhead high-voltage distribution line that has experienced a power outage due to a ground fault, and an explorer moves along the overhead high-voltage distribution line holding a receiver for the carrier signal. If the carrier signal passes through the accident point during the movement process, most of the carrier signal disappears, so a method was devised to detect the disappearance on the display section of the receiver to determine the accident point.

However, with this method, it is difficult to separate the above-mentioned carrier signal from other external induced noise signals, such as noise signals emitted from automobile ignition plugs or from customers on high-voltage distribution lines that have not experienced a power outage. ,
There is a problem in that points that are not accident points are often identified as accident points, or conversely, accident points cannot be found.

In addition to the above method, in order to detect the point of disconnection of underground electric wires, a repetition frequency of 1 to 3K is used.
A low-frequency current of 100 to 200 KHz is sent into the wire as an intermittent Hz wave, while an explorer carrying a locator (receiver) moves along the wire in the same manner as above while looking at the display on the receiver. There is a method of searching for the point of a disconnection accident (Japanese Patent Application Laid-Open No. 53-28285).

However, even if this method is used to detect ground fault points on overhead distribution lines,
A signal with a high frequency of Hz causes a large current to flow into the ground capacitance of the distribution line, regardless of whether it is before or after the ground fault point. For this reason, especially when the ground fault is a high-resistance ground fault, there is no discernible change in the display of the receiver either before or after the ground fault point, making it difficult to identify the ground fault point. There was a problem.

Therefore, in the above method, if the signal sent to the electric wire is an audio frequency signal so that no current flows through the ground capacitance, the lower limit of the signal sent to the electric wire approaches the commercial frequency. Then, the receiver receives a large amount of commercial frequency induced noise regardless of whether it is before or after the fault point, and as mentioned above, there is no discernible change in the display, making it difficult to identify the ground fault point. .

Therefore, if the signal sent to the electric wire is a signal with a frequency below the audible frequency so as not to be affected by the above-mentioned ground capacitance and also not to be affected by the induced noise of the commercial frequency, the above-mentioned repetition frequency becomes extremely low. Become. Then, in the receiver, the movement of the display section in response to this becomes extremely slow. Then, the speed at which the explorer moves while looking at the display must be made extremely slow, which poses the problem of extremely reducing the efficiency of the exploration work.

Therefore, the present invention is intended to solve the above-mentioned problems, and it is possible to easily search for the accident point.
Furthermore, the fault point can be clearly detected regardless of the presence or absence of external noise, and furthermore, the fault point can be reliably searched in the case of a high-resistance ground fault, and furthermore, such search work can be carried out efficiently. The present invention attempts to provide a fault point detection method for overhead power distribution lines.

The drawings showing the embodiments of the present application will be described below. Figure 1 shows the situation in which the accident point is being investigated. 1 is a utility pole, 2 is an overhead high-voltage distribution line,
Shows the distribution line involved in the ground fault. Note that A indicates the accident point. 3 is a transmitter in the exploration device, one of its output ends is connected to the above-mentioned power distribution line, and the other end is grounded. 4 indicates an explorer, and 5 indicates a receiver in the exploration device.

Next, in FIG. 3, which shows the circuit configuration of the transmitter 3 as a block diagram, 10 is a carrier wave oscillation circuit;
10' (FIG. 5 shows FIGS. 3 and 4).
The output waveforms of each circuit represented by each block in the figure are shown. The correspondence is indicated by a symbol with a dash "'". ) is designed to oscillate a sine wave like this. As an example, the frequency is
A frequency of about 100 to 1000 Hz is used, and this can be varied. 11 is a modulated wave oscillation circuit which oscillates a rectangular wave (this may also be a sine wave) as shown in FIG. 5, 11'. As an example, a frequency of about 0.5 to 5 Hz is used, and this frequency can be varied. 12 is a mixing circuit which modulates the signal from the carrier wave oscillation circuit 10 with the signal from the modulated wave oscillation circuit 11 and outputs a signal as shown in FIG. 5, 12'. 13 is a power amplification circuit, and 14 is a matching circuit, which is used to efficiently transfer the output signal of the amplification circuit 13, that is, the exploration signal, to the distribution line 2.

Next, in FIG. 4, which shows the circuit configuration of the receiver 5 as a block diagram, 20 is an antenna, and a frame antenna is used as an example. 21 is an attenuation circuit, 2
Reference numeral 2 denotes a carrier wave filter, which allows a signal having the same frequency as the oscillation frequency of the carrier wave oscillation circuit 10 in the transmitter 3 to pass therethrough. Note that a mechanical filter is used as the filter 22, for example. 23 is a detection circuit for extracting a modulated wave signal from a modulated carrier wave signal, that is, a probe signal. 24 is a modulation wave filter,
A signal having the same frequency as the oscillation frequency of the modulated wave oscillation circuit 11 in the transmitter 3 is allowed to pass through. Reference numeral 25 denotes a DC conversion circuit, which converts the signal (low frequency AC of 0.5 to 5 Hz) passed through the filter 24 into DC. Reference numeral 26 denotes a display unit which displays the presence or absence of a signal from the conversion circuit 25 by, for example, the deflection of a meter and the presence or absence of an audible signal. Note that this display may be performed with or without visible light or by other methods.

Next, the search for an accident point using the above-mentioned search device and the operation of the receiver in that case will be explained. The probe signal is transmitted from the transmitter 3 to the distribution line 2 as shown in FIG.
Meanwhile, the explorer 4 carries the receiver 5 and moves along the power distribution line 2. In this state, in the healthy section B of the distribution line 2, the signal current of the exploration signal flows through the ground fault resistance at the ground fault point, so the exploration signal is received by the receiver 5 as shown in FIG. Then, the output waveform of each circuit in the receiver 5 becomes as shown by a solid line in the range B' in FIG. 5, and the display section 26 displays that the probe signal is detected.

In this case, as shown in A and B, even if a noise signal other than the probe signal is input and it has the same frequency as the carrier signal, 23' and 2
As shown by the waveform 4', the signal is removed when it passes through the modulated wave filter 24, and the signal is displayed on the display section 2.
6 continues to provide a stable indication that a probe signal is being detected.

When the explorer 4 eventually passes the accident point A and reaches section C, the exploration signal is no longer received as shown in FIG. Then, each circuit in the receiver 5 no longer outputs anything as shown by the solid line in the range C' in FIG. 5, and the display section 26 displays that the search signal is no longer detected.

Therefore, while the explorer 4 is moving as described above while looking at the display unit 26 or listening to the sound emitted from the display unit 26, the explorer 4 is in a state where the display unit 26 is displaying the detection of the exploration signal. By finding a change point where the non-detection is displayed, that point can be known as a ground fault point. In the above case, since the exploration signal is a carrier wave signal with a frequency of 100 to 1000 Hz modulated by a modulated wave signal, even if the overhead power distribution line has ground capacitance in section C, the ground Substantially no signal current flows through the capacitance. Therefore, even if the above-mentioned ground fault is a high-resistance ground fault such as a tree contacting an overhead distribution line, a crack in the insulator supporting the overhead distribution line, or a pinhole in the insulation coating of a lead-in cable from the overhead distribution line, the above-mentioned ground fault will not occur. Significant fluctuations appear on the display section 26 of the receiver 5 before and after the ground fault point, making it possible to reliably identify the ground fault point.

Furthermore, even if a noise signal other than the exploration signal is input as shown in c and d at a place past the ground fault point A as described above, that signal is removed and displayed in the same way as in the previous case. The unit continues to display a stable indication that the probe signal is no longer detected.

As described above, in the present invention, while transmitting an exploration signal to the distribution line 2 involved in the accident, the receiver 5 is moved along the distribution line 2 involved in the accident, and the exploration signal entering the receiver 5 is transmitted. Since the fault point is discovered by detecting signal fluctuations, the explorer 4 who is investigating the fault can very easily and accurately locate the fault point A by simply moving along the distribution line 2 involved in the fault. There are features that can be found. Moreover, the present invention uses a signal obtained by modulating a carrier signal with a modulating wave signal as a search signal, and on the other hand, on the side of the receiver 5, the signal received by the antenna 20 is passed through both the carrier wave filter 22 and the modulating wave filter 24. , and the display is performed by the signals transmitted through them. Therefore, when investigating the accident point as described above, the antenna 20 carried by the explorer 4 receives not only the above-mentioned exploration signals but also the ignition of the car. Even if signals emitted from faucets or signals called externally induced noise emitted from customers who are not experiencing a power outage are received one after another, and the signals received by the antenna 20 greatly increase or decrease, the above-mentioned explorer 4
While moving in a healthy section B on the distribution line 2, the display unit 26 continues to display a stable display without being disturbed by the large increase or decrease in the signal received by the antenna 20. When the point A is reached, even if the antenna 20 receives a large number of various signals other than the search signal in exactly the same way as in the healthy section, the display on the display unit 26 will not be confused by such signals. This has the effect that the fault point A on the distribution line 2 can be clearly displayed.

This not only makes it possible to see the display accurately when the display section 26 is an analog display such as a meter, but also allows the display section 26 to be viewed accurately.
is a display device that uses audible sound or visible light (the display only changes depending on the presence or absence of a signal, and even if the amount of the signal changes, it does not give a big impression to humans) Even if it is a display device), it has a remarkable effect of making the fluctuation of the display noticeable (so that it is easy to distinguish whether it is an accident point or not) and clearly informing the explorer 4. be. Furthermore, in the present invention, ground faults are caused by high resistance ground faults such as contact of trees with overhead distribution lines, cracks in the insulators supporting overhead distribution lines, or pinholes in the insulation coating of cables leading from overhead distribution lines. When searching for the ground fault point in a case, the detection signal to be placed on the overhead distribution line 2 is that the signal current flows through the ground fault resistance in the section before the ground fault point, and the signal current flows through the ground fault resistance in the section after the ground fault point. Even if there is a ground capacitance in the overhead distribution line, the plate transmission signal with a frequency of 100 to 1000 Hz is modulated by a modulated wave signal so that virtually no signal current flows through the ground capacitance. Since the detected detection signal is used, there is an effect that the display on the display section 26 changes noticeably before and after the ground fault point, making it possible to identify the fault point.

Furthermore, in the present invention, the frequency of the carrier wave signal is selected to be 100 to 1000 Hz, which is higher than the commercial frequency, and the frequency of the modulated wave signal is selected to be 0.5 to 5 Hz, which is lower than the commercial frequency. This has the effect of eliminating commercial frequency induced noise in the receiver regardless of whether it is before or after the accident point, and making it possible to clearly identify the accident point as described above.

Furthermore, since the frequency of the carrier wave signal is selected to be higher than the commercial frequency as described above, a relatively high frequency can be used as the frequency of the modulated wave signal, which is selected to be lower than the commercial frequency. This has the effect that the response of the display section is fast, and therefore the speed of movement of the explorer is correspondingly fast, which can improve the efficiency of exploration work.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and Fig. 1 shows the state of investigation of the accident point, Fig. 2 shows the change in the reception level of the exploration signal in the receiver, and Fig. 3 shows the block of the transmitter. The circuit diagram, Figure 4 is a block circuit diagram of the receiver, and Figure 5 is a diagram showing the output waveforms of each circuit in the transmitter and receiver. showed that). 2... Overhead distribution line, 3... Transmitter, 4... Explorer, 5... Receiver, 20... Antenna, 22...
Carrier wave filter, 24...Modulation wave filter.

Claims (1)

[Claims] 1. In the fault point detection method for overhead distribution lines, which transmits an exploration signal to the overhead distribution line involved in the accident and searches for the ground fault point by moving a receiver along the distribution line involved in the accident, the above-mentioned exploration The signal is higher than the commercial frequency, output from a carrier oscillator.
A carrier signal with a frequency of 100 to 1000Hz is output from a modulated wave oscillator, which is 0.5 to 100Hz lower than the commercial frequency.
A signal modulated by a modulated wave signal with a frequency of 5 Hz is used.Meanwhile, in the receiver, the antenna receives the exploration signal from the power distribution line, and the signal received by the antenna is transmitted to the carrier wave filter and the modulated wave signal. The signals passed through these filters are converted to DC by a DC conversion circuit, and the display is made to respond to the DC-converted signals, thereby reducing the large change in the display that appears on the display during the movement process. A fault point detection method for an overhead power distribution line, characterized in that by finding a point, the change point is searched as a fault point.